This invention generally relates to an electrical panelboard. More specifically, this invention relates to a combination of an insulating base pan and bus bars.
As with many electrical apparatus, a common goal is to reduce the size of the apparatus without reducing the voltage and current ratings of the apparatus. Additionally, when the size and/or configuration of an apparatus are modified, standards such as Underwriter Laboratory standards must be met. For example, in a three phase load center the bus bars must be spaced such that arcing in avoided between the bus bars at the rated voltage and current of the load center.
One mode of arcing between the bus bars of a multi-phase system is in the form of an arc which follows a path along the surfaces of the base pan supporting the bus bars. To prevent this type of arcing, minimum "cross surface clearances" are required between bus bars for a given voltage and current rating. In general, the "cross surface clearance" is the distance between the bus bars measured along a path lying upon the base pan, wherein the path is substantially perpendicular to the bus bars. Accordingly, if the width of a base pan supporting parallel bus bars is to be reduced, steps must be taken so that the cross surface clearances between the bus bars are adequate.